In this paper,the static pressure measurement error at the wall tap at the throat of the flow nozzle is examined for a wide range of Reynolds number. The error is estimated using the measured discharge coefficients for different wall tap diameters. The differential pressure measurement error is clearly influenced by the diameter of the wall tap and the viscosity of the working fluid. To obtain a universal relation,several relations between the static pressure measurement error divided by the wall shear stress and the tap Reynolds number are presented. The best relation to reasonably explain the static pressure measurement error for the wall tap at the throat of the flow nozzle is expressed by the function (eL/τw)(dt/d)–0.5 and the tap Reynolds number by uτdT/ν. This relation might be useful for estimating the value of the static pressure measurement error not only for the wall tap at the throat of the flow nozzle but also for the inlet pipe flow. Moreover ,this relation also available to estimate the static pressure measurement error for the wall tap with large diameter